Systems and methods for power optimized framing

ABSTRACT

Power dissipation within a network service unit, such as digital-subscriber-line access multiplexer (DSLAM), is treated as a resource that is to be shared among subscribers. In this regard, the total amount of available power dissipation is quantified, and the framing for the data streams communicated across the subscriber lines are controlled to ensure that specified power dissipation limits are not exceeded, accounting for one or more factors, such as traffic load, service level agreement (SLA) specifications, available power, and temperature.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/691,128, entitled “Power Optimized Framing,” and filed on Aug.20, 2012, which is incorporated herein by reference.

RELATED ART

In a telecommunication system, a network service unit often resides atan intermediate point, such as a distribution point (DP), between one ormore customer premises (CP) and a network facility, such as a centraloffice (CO). On the network side, the service unit is typicallyconnected to at least one network connection, such as an optical fiber,extending from a network facility. On the CP side, the service unit istypically connected to a plurality of subscriber lines servicing one ormore customer premises, and the service unit provides a networkinterface for the CP traffic. In a digital-subscriber-line (DSL)architecture, such a service unit is sometimes referred to as a DSLaccess multiplexer or “DSLAM.”

A network service unit can be deployed in an outside plant environmentat any of various points between customer premises equipment (CPE) and anetwork facility. Thus, a network service unit often has anenvironmentally-hardened housing in which the electrical components ofthe service unit are situated. Such housings are typically composed ofthermally conductive materials and have power sinking features, such asfins, incorporated into their designs in an effort to remove heat fromthe electrical components within the housing. However, under someconditions, temperatures within the housing approach or exceed desiredtemperature limits, particularly in warm climates, resulting inperformance issues and sometimes damage to the circuitry within thehousing.

In addition, network service units are often deployed at remotelocations where power supplies are not readily available. In such cases,the service unit may be equipped with a battery and/or receive a limitedamount of power from a network connection or subscriber line. Optimizingthe power consumed by the service unit is generally desirable to helpensure that its power requirements are satisfied in addition to keepingthe unit's internal temperatures within a safe operating range.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdrawings. The elements of the drawings are not necessarily to scalerelative to each other, emphasis instead being placed upon clearlyillustrating the principles of the disclosure. Furthermore, likereference numerals designate corresponding parts throughout the severalviews.

FIG. 1 is a block diagram illustrating an exemplary embodiment of atelecommunication system.

FIG. 2 is a block diagram illustrating an exemplary embodiment of anetwork service unit, such as is depicted by FIG. 1.

FIG. 3 is a block diagram illustrating exemplary consecutive frames.

FIG. 4 is a block diagram illustrating an exemplary embodiment of acontroller having dynamic rate allocation logic implemented in software.

FIG. 5 is a block diagram illustrating an exemplary embodiment of anetwork service unit, such as is depicted by FIG. 1.

FIG. 6 is a block diagram illustrating an exemplary frame.

FIG. 7 is a block diagram illustrating an exemplary timeslot allocationfor four subscribers.

FIG. 8 is a block diagram illustrating an exemplary timeslot allocationfor four subscribers in which each subscriber is assigned equal weight.

FIG. 9 is a block diagram illustrating an exemplary timeslot allocationfor four subscribers when two of the subscribers are idle.

FIG. 10 is a block diagram illustrating an exemplary timeslot allocationfor four subscribers.

FIG. 11 is graph showing power per subscriber for various iterations ofan exemplary power distribution algorithm.

FIG. 12 is graph showing weighted power per subscriber for variousiterations of an exemplary power distribution algorithm.

FIG. 13 is graph showing unweighted power per subscriber for variousiterations of an exemplary power distribution algorithm.

DETAILED DESCRIPTION

The present disclosure generally pertains to systems and methods forpower optimized framing. In one exemplary embodiment, power dissipationwithin a network service unit is treated as a resource that is to beshared among subscribers. In this regard, the total amount of availablepower dissipation is quantified, and the framing for the data streamscommunicated across the subscriber lines are controlled to ensure thatspecified power dissipation limits are not exceeded, accounting for oneor more factors, such as traffic load, service level agreement (SLA)specifications, available power, and temperature.

For example, for a given frame, the available power dissipation may befirst distributed among the active subscribers, and then for each activesubscriber further divided into downstream and upstream timeslots. Thepower distribution is performed such that over a sliding window of aspecified time interval, the average power dissipation remains below aspecified limit. Over a shorter time period, however, large amounts ofdata can be transferred thus exhibiting a high peak power dissipationduring that interval. Such an algorithm for controlling powerdissipation allows for high peak power dissipation and correspondinghigh peak data rates, while simultaneously enforcing a low average powerdissipation below a specified limit. The algorithm also allowsindividual subscribers to use more power when other subscribers are idleor have little data to transfer. In addition, the algorithm allows powerdissipation to dynamically move between downstream dominated andupstream dominated, depending on traffic load, while maintaining a lowaverage power dissipation.

FIG. 1 depicts an exemplary embodiment of a telecommunication system 10having a network service unit 15 coupled between at least one networkdevice 17 of a network 19 and at least one CP transceiver (XCVR) 22 atone or more customer premises 25. As an example, the network device 17may reside at a central office or some other facility of the network 19,and the network service unit 15 may reside at a distribution point orsome other intermediate point between the network 19 and the customerpremises 25. In other embodiments, other locations of the network device17 and the network service unit 15 are possible, and the network serviceunit 15 may be used to service any number of CP transceivers 22.Further, the same subscriber may utilize any number of CP transceivers22.

As shown by FIG. 1, the network service unit 15 has a network-sideinterface 33 that is coupled to the network device 17 via a networkconnection 35. In one exemplary embodiment, the network connection 35comprises an optical fiber, but other types of communication media maybe used in other embodiments, such as one or more twisted-wire pairs.

The network service unit 15 also comprises a CP-side interface 37 thatis coupled to the CP transceivers 22 by a plurality of subscriber lines39, respectively. In one exemplary embodiment, each subscriber line 39is implemented as a twisted-wire pair, but other types of communicationmedia, such as optical fiber, are possible in other embodiments. Usingtwisted-wire pairs for the subscriber lines 39 has the advantage ofleveraging existing copper infrastructure for at least the segmentbetween the network service unit 15 and the customer premises 25.Although conductive connections, such as twisted-wire pairs, generallydo not permit data rates as high as other media, such as optical fiber,across long distances, the distances between intermediate points (e.g.,DPs) and the customer premises 25 are relatively short. Also, thetraffic communicated across the network connection 35 may be distributedacross multiple subscriber lines 39 such that it is not necessary foreach subscriber line 39 to support the same peak data rates that aresupported by the network connection 35. In this regard, the networkservice unit 15 comprises a multiplexer (MUX) 42 that is configured tomultiplex the high-speed data stream from the network connection 35across multiple subscriber lines 39, as will be described in more detailhereafter. In the opposite direction, the MUX 42 combines the datastreams from the subscriber lines 39 into a single, high-speed datastream for communication across the network connection 35.

Various communication protocols and formats may be used for thecommunication across the subscriber lines 39 and the network connection35. In one exemplary embodiment, the network connection 35 isimplemented as an optical fiber, and an optical format in accordancewith GPON or GbE is used for communication across the network connection35. In addition, a DSL protocol such asymmetric DSL (ADSL),high-bit-rate DSL (HDSL), HDSL2, very-high-bit-rate DSL (VDSL), fastaccess subscriber terminals (FAST), or other k0nown DSL protocol is usedfor the communication across the subscriber lines 39. However, it shouldbe emphasized that other protocols are possible in other embodiments.

FIG. 2 depicts an exemplary embodiment of the network service unit 15.For the exemplary unit 15 depicted by FIG. 2, the network-side interface33 is implemented via an optical network unit (ONU) 49 that is coupledto the network connection 35, which is implemented as an optical fiberin this embodiment. In such embodiment, the network device 17 (FIG. 1)may comprise an optical line terminal (OLT) coupled to the networkconnection 35 at the opposite end of the connection 35. As shown by FIG.2, the CP-side interface 37 is implemented via a plurality oftransceivers (XCVRs) 52 that are respectively coupled to the subscriberlines 39.

In the downstream direction, the network device 17 transmits ahigh-speed data stream having packets destined for various CPtransceivers 22 across the network connection 35 to the ONU 49. The ONU49 converts the data stream from the optical domain to the electricaldomain and electrically transmits the data stream to the multiplexer 42.The multiplexer 42 multiplexes the packets within the received datastream such that each packet is transmitted to the appropriatetransceiver 52 for communication across the appropriate subscriber line39 to the CP transceiver 22 to which the packet is destined. As known inthe art, the multiplexer 42 may be have a forwarding table (not shown)or other data for indicating which transceiver 52 is to transmit eachpacket based on control information contained in the packet's header.Using such information, the multiplexer 42 identifies which transceiver52 is to transmit a given packet and forwards the packet to suchtransceiver 52. The transceiver 52 then modulates a carrier signal withthe data to form a data signal that is transmitted across the subscriberline 39 that is coupled to the transceiver 52.

In the upstream direction, each CP transceiver 22 transmits a datasignal across its respective subscriber line 39 to the transceiver 52 ofthe service unit 15 that is coupled to such subscriber line 39. Thetransceiver 52 demodulates the data signal to recover a data stream, andthe multiplexer 42 combines the streams from multiple subscriber lines39 into a single, high-speed data stream. The ONU 49 converts suchhigh-speed data stream from the electrical domain to the optical domainfor transmission across the network connection 35 to the network device17 (FIG. 1).

Note that the electrical components of the service unit 15 shown by FIG.2 are situated in an environmentally-hardened housing 60 for protectingthe electrical components from environmental conditions, such as rain,dust, etc. In this regard, the housing 60 preferably encloses theelectrical components and is sealed to prevent water and particles fromentering the housing 60. The housing 60 is preferably composed ofthermally conductive materials that are in contact with the electricalcomponents in an effort to draw heat away from such components.

As shown by FIG. 2, the network service unit 15 comprises dynamic rateallocation (DRA) logic 63 that is configured to dynamically controlframing for the communication occurring across the subscriber lines 39,as will be described in more detail below. In one exemplary embodiment,the framing implements a time division duplex (TDD) architecture whereboth upstream and downstream communication occurs in the same frequencyrange but are separated in time in order to prevent data collisions.

For illustrative purposes, FIG. 3 depicts two consecutive frames forcommunication occurring across a subscriber line 39. Each frame isdivided into a number of timeslots (TS) that can be allocated by the DRAlogic 63 for either downstream transmission or upstream transmission. Inthe exemplary frames shown by FIG. 3, each frame is divided into tentimeslots for simplicity of illustration, but the frames may have anynumber of timeslots in other embodiments.

The DRA logic 63 may allocate a timeslot of a given frame for activedownstream transmission (represented as “D” in subsequent figures) oractive upstream transmission (represented as “U” in subsequent figures).When a timeslot is allocated for active downstream transmission,downstream data may be transmitted during the timeslot by the serviceunit transceiver 52 that is coupled to the subscriber line 39 thatcarries the data. However, the CP transceiver 22 may not transmitupstream data during the timeslot. When a timeslot is allocated forupstream transmission, upstream data may be transmitted during thetimeslot by the CP transceiver 22 that is coupled to the subscriber line39 that carries the data. However, the service unit transceiver 52 maynot transmit downstream data during the timeslot. A timeslot will bereferred to hereafter as “active” when data is or is to be activelytransmitted in the timeslot.

In an effort to optimize communication efficiency, the timeslotsallocated for upstream communication are grouped together and thetimeslots allocated for downstream communication are grouped together sothat there is only one transition from downstream communication toupstream communication per frame. In addition, to mitigate crosstalk,upstream and downstream groups from one subscriber line 39 to the nextare synchronized in order to prevent one subscriber line 39 fromcarrying upstream data while another subscriber line 39 is carryingdownstream data. That is, each frame is segmented into a downstreamgroup, referred to herein as “downstream block,” and an upstream group,referred to herein as “upstream block,” and each timeslot is assigned toa respective one such block. Further, for each frame, the downstreamblock occurs at the same time (i.e., overlaps in time) for eachsubscriber line 39, and the upstream block occurs at the same time(i.e., overlaps in time) for each subscriber line 39.

Note that between consecutive upstream and downstream blocks is aswitching time (ST) period where the service unit transceiver 52 and CPtransceiver 22 are not permitted to actively transmit across thesubscriber line 39. The ST period is preferably of sufficient length toensure that the data transmitted in the last timeslot of a givenupstream or downstream block propagates across the subscriber line 39and is received at the far end of the line 39 before the transceiver (22or 52, depending on the direction of transmission) at the far end of theline 39 is permitted to transmit in the opposite direction. Permittingonly one downstream block and one upstream block per frame minimizes thenumber of these ST periods thereby increasing the amount of time that isavailable for active transmissions.

The DRA logic 63 is configured to communicate with each CP transceiver22 via a control channel so that the DRA logic 63 may inform each CPtransceiver 22 of its timeslot allocation for each frame. As will bedescribed in more detail hereafter, the DRA logic 63 dynamicallyallocates the timeslots based on various factors, such as traffic loadand temperature, and informs each transceiver 22 and 52 of the timeslotsthat have been allocated to it. As an example, the DRA logic 63 maydefine a media access plan (MAP) and communicate such MAP to eachtransceiver 22 and 52 as is done in conventional TDD systems in order tocontrol timeslot allocations.

If desired, the control channel may be provided separate from thesubscriber lines 39, such as a dedicated line (not shown) fortransmitting control information between the service unit 15 and the CPtransceivers 22. In one exemplary embodiment, the control channel isembedded in the data streams transmitted across the subscriber lines 39.As an example, the DRA logic 63 may allocate some downstream andupstream timeslots for control information. The DRA logic 63 may use thedownstream timeslots allocated for control information in order totransmit the MAP described above to the CP transceivers 22. The CPtransceivers 22 may use the upstream timeslots allocated for controlinformation in order to provide various control information, such astraffic load at the CP transceivers 22. For example, a CP transceiver 22may provide a value indicative of the amount of data that the CPtransceiver 22 currently has queued for transmission across itsrespective subscriber line 39. The DRA logic 63 may similarly receivefrom each service unit transceiver 52 a value indicative of the amountof data the service unit transceiver 52 currently has queued fortransmission across its respective subscriber line 39. Thus, the DRAlogic 63 has information indicating the traffic load conditions at eachtransceiver 22 and 52 and uses such information in order to maketimeslot allocation decisions, as will be described in more detailhereafter.

Note that the DRA logic 63 can be implemented in software, hardware,firmware or any combination thereof. In one exemplary embodimentillustrated by FIG. 4, the DRA logic 63 is implemented in software andstored in memory 71 of a controller 73. Note that the DRA logic 63, whenimplemented in software, can be stored and transported on anycomputer-readable medium for use by or in connection with an instructionexecution apparatus that can fetch and execute instructions. In thecontext of this document, a “computer-readable medium” can be any meansthat can contain or store a computer program for use by or in connectionwith an instruction execution apparatus.

The controller 73 depicted by FIG. 4 comprises at least one conventionalprocessing element 76, such as a digital signal processor (DSP) or acentral processing unit (CPU), that communicates to and drives the otherelements within the controller 73 via a local interface 78, which caninclude at least one bus. Furthermore, an input/output (I/O) interface81 enables the DRA logic 63 to communicate with components external tothe controller 73 shown by FIG. 4.

The DRA logic 63 is configured to control timeslot allocation in orderto ensure that the average power dissipation during a specified timeinterval does not exceed a threshold, referred to hereafter as TH_(P).Such threshold TH_(P) can be set based on various factors. As anexample, the threshold can be set to ensure that the power consumed bythe service unit 15 does not exceed the power that is available forconsumption. Alternatively, the threshold can be set to ensure thatoperating temperatures within the service unit 15 remain within adesired range in an effort to prevent overheating conditions within theunit 15. Other reasons for controlling power dissipation are possible.

The DRA logic 63 is preferably configured to dynamically adjust thetimeslot allocations in an effort to optimize the framing structure inorder to efficiently and fairly share the available power dissipationacross a plurality of subscribers. In one exemplary embodiment, the DRAlogic 63 uses principles similar to known max-min fairness or othersimilar algorithms to assign timeslots in an efficient and fair mannerwhen power dissipation constraints and traffic demand cause congestion.

In this regard, each subscriber serviced by the unit 15 is assigned aweight, and the DRA logic 63 allocates available power (which can belimited by the power constraints described herein) among the subscribersbased on the respective weights assigned to the subscribers. Forinstance, if each subscriber has a backlog of traffic to be transmittedfor a given frame, the DRA logic 63 may allocate more power fortransmission/reception to subscribers that are assigned a higher weightand less power for transmission/reception to subscribers that areassigned a lower weight. Thus, a subscriber assigned a higher weight maybe allowed to dissipate more power during a frame.

Once the DRA logic 63 has established an amount of power that asubscriber is allowed to dissipate in a given frame, the DRA logic 63allocates timeslots for the subscriber based on the subscriber's powerlimit for the frame. For example, the DRA logic 63 may allocate to thesubscriber as many active upstream and/or downstream timeslots as ispossible within the framing structure without exceeding the subscriber'spower limit for the frame. In this regard, each active timeslot within aframe causes a certain amount of power dissipation at the service unittransceiver 52 that processes the data communicated in the timeslot, andthe DRA logic 63 ensures that the sum of the power dissipated by thetransceiver 52 servicing a particular subscriber does not exceed thepower limit specified for the subscriber. Thus, for a given frame, thetotal number of active timeslots allocated to a subscriber is based onand, specifically, limited by the power limit assigned to the subscriberfor the frame. Moreover, for a given frame, a subscriber assigned ahigher weight may be allocated a higher dissipation and, hence, moretimeslots relative to a subscriber assigned a lower weight. However, aswill be described in more detail, there may be exceptions based ontraffic demand and other factors.

In one exemplary embodiment, the memory stores 71 stores controlparameters 88 (FIG. 4) that the DRA logic 63 uses to allocate timeslots.As an example, the control parameters 88 may indicate the weightsassigned to the subscribers serviced by the unit 15. Such parameters 88are preferably provisioned by a technician or other user based on therespective SLAs for the subscribers and/or other factors.

Note that the service unit 15 has a plurality of ports that arerespectively coupled to the subscriber lines 39. Each port has anidentifier, referred to as “port identifier,” identifying the port and,hence, the subscriber line 39 to which the port is coupled. The controlparameters 88 may associate the weights with port identifiers toindicate which port and, hence, subscriber line 39 is associated with arespective weight. Identifying the port that is used to service asubscriber has the effect of identifying the subscriber line 39 and thetransceiver 52 that are coupled to the port. In the context of thisdocument, indicating that power is allocated to a particular subscriberhas the same meaning as allocating the power to the transceiver 52 thatis used to service the subscriber. That is, when a power unit isdescribed herein as being allocated to a subscriber, the transceiver 52coupled to the line 39 associated with the subscriber is permitted todissipate an amount of power up to the value of the allocated powerunit. In other words, the power unit is allocated to such transceiver52, which has the effect of increasing the number of upstream and/ordownstream timeslots processed by the transceiver 52.

The DRA logic 63 preferably optimizes the power distribution amongsubscribers in order to account for traffic load and other factors. Forexample, assume that a subscriber having a relatively high weight doesnot have enough data queued for transmission in order to utilize eachtimeslot that would otherwise be allocated to the subscriber based onthe respective subscriber weights. In such case, the DRA logic 63 may beconfigured to allocate less power and, therefore, assign fewer timeslotsto the subscriber, thereby decreasing the number of timeslots allocatedto the subscriber for a given frame and increasing the number oftimeslots allocated to one or more other subscribers that have a backlogof data queued for transmission. Exemplary timeslot allocationalgorithms will be described in more detail below.

In addition, the DRA logic 63 is configured to adjust the powerdissipation constraints over time based various runtime factors suchthat the power dissipation and, hence, total number of timeslotsallocated for active transmissions can change from one frame to thenext. In one exemplary embodiment, such adjustments are based ontemperature. In this regard, as shown by FIG. 2, the service unit 15 hasat least one temperature sensor 94 for sensing a temperature of the unit15. For example, in FIG. 2, a respective temperature sensor 94 iscoupled to each transceiver 52 for measuring a temperature of thetransceiver 52 to which it is coupled. A temperature sensor 94 may becoupled to the housing 60 for measuring a temperature of the housing 60or the ambient temperature external to the housing. A temperature sensor94 may be coupled to any component of the service unit 15 in otherembodiments.

The DRA logic 63 is configured to monitor the temperature measurementsfrom at least one temperature sensor 94. If the sensed temperatureexceeds a predefined upper temperature threshold, the DRA logic 63 isconfigured to reduce the power limit (e.g., TH_(P)) so that the averagepower dissipation decreases. That is, the DRA logic 63 is configured toreduce the power limit such that, on average, the amount of powerallocated to each frame is less, thereby resulting in fewer activetimeslots per frame on average. Thus, when the measured temperaturereaches a specified level, the average power dissipated by the serviceunit 15 is reduced in an effort to keep the temperature within a desiredoperating range.

Once the sensed temperature falls below a predefined lower temperaturethreshold, the DRA logic 63 is configured to increase the power limit(e.g., TH_(P)) so that, on average, the amount of power allocated toeach frame is greater, thereby resulting in a higher number of activetimeslots per frame on average. Accordingly, the power dissipation limitcan be increased during times of relatively low temperature in order topermit higher data rates, and the power dissipation limit can be laterdecreased as temperature rises in order to prevent overheatingconditions within the service unit 15. Thus, the allowed powerdissipation is optimized based on temperature in order to allow higherdata rates when conditions permit such increases while ensuring that thedata rate increases do not result in overheating conditions within theservice unit 15.

In other embodiments, the power dissipation can be similarly optimizedbased on other conditions and factors, such as power availability. FIG.5 shows an exemplary embodiment of a service unit 15 having powercircuitry 101 coupled to a plurality of subscriber lines 39. The powercircuitry 101 is configured to receive at least one power signal from atleast one subscriber line 39 and/or other external source and to harnesspower from such signals in order to provide electrical power to at leastone component of the service unit 15. The power circuitry 101 mayaggregate power from multiple subscriber lines 39. The power circuitry101 may also use such power to provide a conditioned and regulated apower signal for use in powering components of the service unit 15.Exemplary techniques for powering a service unit from power signalstransmitted across subscriber lines 39 are described incommonly-assigned U.S. patent application Ser. No. 12/839,403, entitled“Systems and Methods for Powering a Service Unit” and filed on Jul. 19,2010, which is incorporated herein by reference.

The power circuitry 101 is configured to transmit to the DRA logic 63information indicative of an amount of power received from thesubscriber lines 39 and other external sources, if any. As an example,the power circuitry 101 may be configured to sense an amount (e.g.,voltage and/or current) of electrical power received from the subscriberlines 39 and provide a value indicative of such sensed amount. Inanother embodiment, the power circuitry 101 may determine a number ofsubscriber lines 39 that are actively providing power above a predefinedthreshold and inform the DRA logic 63 of such number. Based on thisnumber, the DRA logic 63 may estimate the amount of electrical powerreceived. Alternatively, the number of subscriber lines 39 expected toprovide power may be provisioned into the control parameters 88 (FIG.4). In other embodiments, other types of information indicative of theamount of electrical power received from external sources or otherwiseavailable for use in the service unit 15 are possible.

Based on the information indicative of the total power available, theDRA logic 63 is configured to determine a power dissipation limit forensuring that the power dissipated by the service unit 15 is less thanthe amount of power available. As an example, the DRA logic 63 mayadjust the power limit (e.g., TH_(P)) based on the information from thepower circuitry 101. Thus, the DRA logic 63 is configured to control thenumber of timeslots in each frame allocated for active transmission inorder to ensure that the average power dissipated over a given timeinterval is less than the average power available during such timeinterval.

Note that there are various approaches that can be used to ensure thataverage power dissipated remains below a specified power limit (e.g.,TH_(P)). For example, the DRA logic 63 may be configured to maintain thesame per-frame power limit for all of the frames. In another embodiment,the DRA logic 63 is configured to change the power limit per frame butto ensure that the power limits are selected such that, over apredefined time interval spanning multiple frames, the average powerdissipated does not exceed the power limit (e.g., TH_(P)). This has theeffect of allowing peak data rates during certain times, such as periodsof high congestion, while ensuring that the data rates are reducedduring other time periods in order to ensure that the specified powerconstraint over time is not violated.

Specifically, during a frame for which there is a relatively largeamount of data queued for transmission across the subscriber lines 39,the DRA logic 63 may be configured to specify a relatively high powerlimit and, hence, allocate a relatively large number of activetimeslots, thereby increasing the data rate for such frame. Such powerlimit may be sufficiently high such that, if the same power limit isused for all frames, then the power constraint could be violated.However, over a specified time interval inclusive of such frame, the DRAlogic 63 is configured to allocate a lower power limit for one or moreframes to ensure that the average power actually dissipated during thetime interval is less than the specified power constraint (e.g.,TH_(P)). Thus, in effect, the DRA logic 63 defines a sliding window of aspecified duration across the frames and ensures that the total powerdissipated during the window is sufficiently low to ensure that thepower constraint is not violated while allowing some of the frames tohave a relatively high power dissipation limit.

Note that the power limits described herein may be specified in avariety of ways. For example, a power limit may be a predefined valuethat is stored in memory and provisioned by a technician or other user.Alternatively, a power limit may be calculated by the DRA logic 63 orother component based on one or more factors, such as temperature. Inother embodiments, other techniques for specifying a power limit arepossible.

It should be further noted that the DRA logic 63 may adjust the sizes ofthe upstream and downstream blocks based on traffic load or otherfactors. For example, when a relatively large amount of traffic isqueued at the CP transceivers 22, the DRA logic 63 may increase theupstream block, thereby increasing the total number of timeslotsavailable for upstream transmissions, and decrease the downstream blockby a corresponding amount, thereby decreasing the total number oftimeslots available for downstream transmissions. Conversely, when arelatively large amount of traffic is queued at the service unittransceivers 52, the DRA logic 63 may increase the downstream block,thereby increasing the total number of timeslots available fordownstream transmissions, and decrease the upstream block by acorresponding amount, thereby decreasing the total number of timeslotsavailable for upstream transmissions.

An algorithm for ensuring that the power constraint is not violated maytake into account frame-to-frame changes in the relative numbers ofactive upstream and downstream slots. In this regard, each service unittransceiver 52 likely dissipates a different amount of power to transmitdata in a downstream timeslot relative to receiving data in an upstreamtimeslot. Thus, even if the total number of active timeslots are thesame for any two given frames, the total power dissipated by a serviceunit transceiver 52 is likely different for each frame if the ratio ofactive upstream timeslots to active downstream slots is different. Inone exemplary embodiment, the DRA logic 63 takes into accountdifferences in such ratios from one frame to the next in order to ensurethat the power constraint is not exceeded.

For example, the control parameters 88 (FIG. 4) may be provisioned inorder to indicate the amount of power dissipated by each transceiver 52to transmit data in a downstream timeslot and the amount of powerdissipated by each transceiver 52 to receive data in an upstreamtimeslot. The control parameters may also be configured to indicate thetotal amount of power dissipated by the other components (e.g., ONU 49and multiplexer 42) of the service unit 15 over a given time interval,noting that such power dissipation may be treated as a constant. The DRAlogic 63 uses such information to ensure that the defined power limit isnot violated over time.

For example, the DRA logic 63 may determine the total power dissipatedso far by the service unit 15 for a given window of time, noting thatthe amount of power dissipated in a frame is based on the number ofactive upstream timeslots in the frame and the number of activedownstream timeslots in the frame. Specifically, the DRA logic 63 maysum three power values to determine the total power dissipated for agiven frame. One power value is a predefined constant representing thepower dissipated by the common components of the unit 15 (i.e.,components other than transceivers 52), such as the ONU 49 (FIG. 2) andthe multiplexer 42, during the frame. Another value is a variabledownstream power value representing the power dissipated by thetransceivers 52 in transmitting downstream, which is a function of thetotal number of active downstream timeslots in the frame. The last valueis a variable upstream power value representing the power dissipated bythe transceivers 52 in receiving upstream, which is a function of thetotal number of active upstream timeslots in the frame.

After determining the total power dissipated so far in a window, the DRAlogic 63 may calculate the amount of power that may be dissipated in theremaining portion of the window in order to ensure that the averagepower dissipated in the window does not exceed the power limit (e.g.,TH_(P)). Such analysis takes into account the amount of power dissipatedfor each active timeslot, which is different depending on whether theactive timeslot is for upstream or downstream.

Note that various modifications to the above-described algorithm. Forexample, since power value for the common components can be treated as aconstant, it is possible to omit this value from the analysis anddetermine value indicative of the total power dissipated by thetransceivers 52. In such an embodiment, a lower power limit may be usedto account for the fact that the value representing the commoncomponents is not summed. Yet other modifications are possible.

To help illustrate some of the foregoing concepts, several specificexamples of techniques and algorithms for ensuring that the averagepower dissipated over a defined time interval remains below a specifiedpower constraint.

For illustrative purposes, assume that the DRA logic 63 defines theframing structure shown by FIG. 6, where T_(cycle) is the period of aframe, T_(DS) is the period of the downstream block within the frame,T_(US) is the period of the upstream block within the frame, M is thetotal number of downstream timeslots in the frame, N is the total numberof upstream timeslots in the frame, and T_(TS) is the period of a singletimeslot. As shown by FIG. 6, the exemplary frame has a sequence of Mdownstream timeslots followed by an ST period, then a sequence of Nupstream timeslots followed by another ST period. As noted above, therespective sizes of the downstream and upstream blocks may change fromframe-to-frame depending on traffic demand. That is, the values of N andM may change over time.

As noted above, the transceivers 22 and 52 are synchronized such thatthe downstream blocks and the upstream blocks respectively overlap forall subscriber lines 39. This is shown in an example depicted by FIG. 7for four subscribers or ports (1-4), where there are 5 downstreamtimeslots per frame and 5 upstream timeslots per frame. All of thedownstream timeslots overlap in time, and all of the upstream timeslotsoverlap in time. Note that some of the timeslots are inactive eitherbecause there is no data to send in the timeslot or because it isdesirable to prevent data from being transmitted in the timeslot inorder to satisfy a constraint, such as a power dissipation limit.

Once the DRA logic 52 determines the power limit for a given frame, theDRA logic 52 distribute the available power for the frame amongsubscribers according to a desired control algorithm. In one exemplaryembodiment, such control algorithm is based on predefined weightsrespectively assigned to the subscribers, as indicated by the controlparameters 88 (FIG. 4). As an example, assume that there are foursubscribers (1-4) where each subscriber is serviced by a singlerespective subscriber line 39. Also, assume that (1) all foursubscribers are weighted equally, (2) there are five downstreamtimeslots for each subscriber in the downstream block, (3) there arefive upstream timeslots for each subscriber in the upstream block, (4)the DRA logic 63 has determined that, in order to satisfy the specifiedpower constraint, a given frame is to be allocated 20 active timeslotsin either the upstream or downstream directions, (5) each transceiver 22and 52 has more than 5 timeslots of data to transmit across thesubscriber lines 39, and (6) there is currently a greater backlog oftraffic queued for the downstream relative to the traffic queued forupstream. For simplicity of illustration, it is assumed that the powerdissipated by the service unit 15 for an active downstream timeslot isthe same as the power dissipated by the service unit 15 for an activeupstream timeslot.

FIG. 8 shows an exemplary timeslot allocation defined by the DRA logic63 for the instant example in which active timeslots are shaded andempty timeslots are not shaded. Note that FIGS. 8-10 do not shown TSperiods for simplicity of illustration, but TS periods are preferablyincluded, as shown by FIG. 6. As can be seen by viewing FIG. 8, eachtransceiver 52 is allocated the same number (i.e., three) of activedownstream timeslots and the same number (i.e., two) of active upstreamtimeslots. Note that a greater number of active timeslots are allocatedto the downstream direction relative to the upstream direction. In otherframes, such as when a greater backlog of traffic exists for theupstream direction, a greater number of active timeslots may beallocated to the upstream direction relative to the downstreamdirection, if desired.

FIG. 9 shows another exemplary timeslot allocation based on the sameassumptions except that two subscribers (i.e., subscribers 3 and 4) areidle. That is, there is no queued data for transmission across two ofthe subscriber lines 39. In such case, no power and, therefore, noactive timeslots are allocated for subscribers 3 and 4, and the powerthat would otherwise have been allocated for subscribers 3 and 4 isinstead distributed across subscribers 1 and 2 equally such that all ofthe timeslots for subscribers 1 and 2 are active.

FIG. 10 shows another exemplary timeslot allocation based on the sameassumptions as for FIG. 8 except that each of the subscribers 2 and 4has sufficient data queued in the downstream direction to occupy onlytwo timeslots and each of the subscribers 1 and 3 has sufficient dataqueued in the upstream direction to occupy only one timeslot. In suchcase, one less downstream timeslot is assigned to each subscriber 2 and4, thereby providing two additional downstream timeslots (relative toFIG. 8) that are allocated equally among subscribers 1 and 3.Additionally, one less upstream timeslot is assigned to each subscriber2 and 4, thereby providing two additional downstream timeslots (relativeto FIG. 8) that are allocated equally among subscribers 1 and 3. Anexemplary algorithm for limiting power dissipation can be describedmathematically, as illustrated below. In this regard, let:

N=number of subscribers connected to the DP

N_(d,i,j)=the number of downstream frames allocated to subscriber “i”during frame “j” (actual)

N_(u,i,j)=the number of upstream frames allocated to subscriber “i”during frame “j” (actual)

K_(d,i)=value representing the power per downstream frame for subscriber“i” (vendor-specified)

K_(u,i)=value representing the power per upstream frame for subscriber“i” (vendor-specified)

P=value representing the maximum average power per frame (computed)

A_(i)=value representing the actual average power per frame forsubscriber “i” (computed)

K=number of frames over which average computed (provisioned)

F=current frame index (increments by one every frame)

C=power associated with common circuitry in DP (vendor-specified)

An exemplary power conservation criterion is:

$\begin{matrix}{P \geq {C + {\frac{1}{K}{\sum\limits_{i = 1}^{N}\; {\sum\limits_{j = {F - K + 1}}^{F}\; {K_{d,i}N_{d,i,j}}}}} + {K_{u,i}N_{u,i,j}}}} & (1)\end{matrix}$

In other words, over all N users and over the K most recent frames,allocate timeslots such that the average power per frame is less than orequal to P. In order for this equation to be enforced, the DP preferablyhas knowledge of the allocated timeslots and has control over at leastsome of the timeslot allocations. The value K_(d,i) and K_(u,i) includethe subscriber index because subscribers on longer loops or with otherimpairments will likely require more power per timeslot than subscriberson “easier” loops.

The power conservation criterion can be rewritten as:

$\begin{matrix}{{P \geq {C + {\frac{1}{K}{\sum\limits_{i = 1}^{N}\; A_{i}}}}}{where}} & (2) \\{A_{i} = {{\frac{1}{K}{\sum\limits_{j = {F - K + 1}}^{F}\; {K_{d,i}N_{d,i,j}}}} + {K_{u,i}N_{u,i,j}}}} & (3)\end{matrix}$

If there is power “congestion” (in other words, if filling the entireframe for all subscribers with timeslots will cause the value of P to beexceeded), then there should be a “fair” way of allocating timeslots tousers.

An exemplary fairness algorithm is to assign each subscriber a “weight”,and allocate the power dissipation such that the ratio of allocatedpower is proportional to the weight assigned. In other words, for weightw_(i) assigned to subscriber “i”,

$\begin{matrix}{\frac{A_{i}}{w_{i}} = \frac{A_{j}}{w_{j}}} & (4)\end{matrix}$

for subscribers “i” and “j” with data to send.

These weights can be assigned to a given subscriber, for example,according to a service level agreement.

As indicated above, for any given frame, it is possible for a particularsubscriber to be allocated more (or less) power and, hence, a higher (orlower) number of active timeslots than what is indicated by its relativeweighting. For instance, if all subscribers are weighted equally, it ispossible for a particular downstream transceiver 52 to be allocated moreor fewer active downstream timeslots than another downstream transceiver52 for a given frame based on traffic demand. In addition, the powerdissipated by one transceiver 52 for transmitting (or receiving) datafor a single timeslot may be different than the power dissipated byanother transceiver 52 due to a variety of reasons, such as differencesin line conditions. Thus, even if each subscriber is assigned the sametimeslot allocation as another subscriber for a given frame, it ispossible for the transceiver 52 servicing one subscriber to dissipate anamount of power that is different than that dissipated by thetransceiver 52 servicing another subscriber during the frame.

In one exemplary embodiment, the DRA logic 63 is configured to track thepower dissipation per subscriber over a window of time spanning multipleframes and attempt to enforce the weighting indicated by the controlparameters 88 (FIG. 4) over time such that the total power dissipationper transceiver 52 over the entire window is close to the transceiver'sproportion indicated by its assigned weight. Thus, in making timeslotallocation decisions for a given frame, the DRA logic 63 takes intoaccount power dissipation totals from previous frames in order tocompensate for disproportionate power dissipation (relative to theweighting indicated by the control parameters 88) that occurredpreviously in the window due to variations in traffic demand over timeor otherwise.

In this regard, in making timeslot allocation decisions for a givenframe, the DRA logic 63 is configured to sum, for each transceiver 52,the total amount of power dissipated for the previous frames in thewindow. The DRA logic 63 is further configured to compare the sums tothe weighting indicated by the control parameters 88 (FIG. 4) and toassign timeslots for the current frame based on the comparison. As anexample, assume that the weighting is equal for all subscribers but thatsubscriber 1 has previously dissipated more power during the windowrelative to subscriber 2. Also assume that both subscribers 1 and 2 havemore data queued for transmission than is possible to transmit duringthe current frame. In such case, the DRA logic 63 may be configured toallocate more power and, hence, assign more timeslots to subscriber 2than to subscriber 1 in order to compensate for the fact that subscriber1 has previously dissipated disproportionately more power during thewindow.

To better illustrate the foregoing, assume that subscribers 1-4 areweighted equally and that the power previously dissipated by thetransceivers 52 of the four subscribers over a window of K frames isindicated by FIG. 11. Specifically, over the past K-1 frames, thetransceiver 52 servicing subscriber 1 has dissipated about 5 units ofpower, the transceiver 52 servicing subscriber 2 has dissipated about 8units of power, the transceiver 52 servicing subscriber 3 has dissipatedabout 10 units of power (i.e., twice as much as subscriber 1), and thetransceiver 52 servicing subscriber 4 has dissipated about 4 units ofpower. The power sum over all four subscribers is 27 units (i.e.,4+10+8+5). Assume further that the power limit for the entire window ofK frames is 34. Thus, there are 7 available power units to be fairlydistributed among the four subscribers. Also, assume that all foursubscribers have queued data to send both upstream and downstream suchthat there are no adjustments to the timeslot allocations based ontraffic demand for the current example.

Assuming that the subscribers are weighted equally, the DRA logic 63performs the power allocation by first effectively “pouring” power intoor allocating power to the lowest power subscriber (i.e., subscriber 4in this example) until this subscriber's power is even with the nextlowest power subscriber (i.e., subscriber 1 in this example). This means1 power unit is effectively “poured” into or allocated to subscriber 4.Once a power unit is allocated to a subscriber, the DRA logic 63 may beconfigured to allocate timeslots to this subscriber commensurate withthe amount of additional power allocated, as will be described in moredetail below.

This approach of allocating the power units to the lowest powersubscribers is repeated until all subscribers are even or until allavailable power units are allocated. Thus, in the instant example, thenext two lowest subscribers (i.e., subscribers 1 and 4 in this example)are equally allocated power units until they reach the next lowest powersubscriber (i.e., subscriber 2 in this example). This means 3 powerunits are effectively “poured” into or allocated to each of thetransceivers 52 servicing subscribers 1 and 4. At this point there areno more power units to allocate, and the power allocation process endswith subscriber 4 allocated 4 power units and subscriber 1 allocated 3power units for the current frame. Accordingly, the total powerdissipated over all K frames of the window is closer to the weightingassigned to all four subscribers relative to the total power dissipatedover the K-1 previous frames. Specifically, the transceivers 52servicing subscribers 1, 2, and 4 dissipate 8 units of power over the Kframes, and the transceiver 52 servicing subscriber 3 dissipates 10units of power. Further, for the current frame, the subscriber 1 isallocated a number of active timeslots (upstream and/or downstream) thatcause the transceiver 52 servicing subscriber 1 to dissipate about(without exceeding) three units of power, and subscriber 4 is allocateda number of active timeslots (upstream and/or downstream) that cause thetransceiver 52 servicing subscriber 4 to dissipate about (withoutexceeding) four units of power. No active timeslots are allocated tosubscribers 2 and 3.

Note that the iterative process described above for allocating powerunits generally continues until the total power allocated over K framesreaches the power limit for the window. However, if a sufficient amountof power has been allocated to a given subscriber to transmit all of itsqueued data (i.e., data that is queued for transmission across thesubscriber's line 39), then the power allocated to such subscriber iscapped. In this regard, after allocating power to a subscriber during aniteration, the DRA logic 63 allocates a number of active downstreamtimeslots to such transceiver 52 servicing the subscriber and/or anumber of active upstream timeslots to the CP transceiver 22 incommunication with such transceiver 52 in order to utilize theadditional power allocated to the subscriber. That is, if x amount ofpower is newly allocated to a transceiver 52 servicing a subscriber,then additional active timeslots (upstream and/or downstream) areallocated to such subscriber, thereby increasing the power dissipated bythe subscriber's transceiver 52, such that the total power dissipated bythe transceiver 52 in processing the additional active timeslots isclose to but not exceeding x. If a point is reached where the allocatedtimeslots are sufficient to transmit all of the data queued for thesubscriber, then no more timeslots are allocated to the subscriber forthe current frame, and any remaining power that has been or would havebeen otherwise allocated to such subscriber by the power allocationalgorithm may instead be allocated to other subscribers according to thetechniques described above.

Similarly, if a point is reached where all timeslots in a frame for agiven subscriber are active, no more power is allocated to suchsubscriber, and any remaining power that has been or would have beenotherwise allocated to such subscriber by the power allocation algorithmmay instead be allocated to other subscribers according to thetechniques described above.

In one exemplary embodiment, the DRA logic 63 is generally configured toimplement the power allocation algorithm described above, but the DRAlogic 63 is configured to ensure that a required minimum number ofdownstream and upstream capacity is provided to each subscriber in everyframe. To effectuate this, the DRA logic 63 first allocates theavailable power units evenly across all subscribers until a givensubscriber's minimum requirement is fulfilled. Once the subscriber'sminimum requirement is fulfilled, no further power units are allocatedto such subscriber until the minimum requirements are fulfilled for allsubscribers serviced by the unit 15. Once the minimum requirements forall subscribers are fulfilled, the DRA logic 63 is configured toallocate any remaining power units according to the algorithm previouslydescribed above.

If the subscribers are weighted differently, then the exemplaryalgorithm described above can be modified to accommodate the differentweighting. As an example, assume that the power previously dissipated bythe subscribers for the previous K-1 frames is the same as describedabove (i.e., 5, 8, 10, and 4 power units for subscribers 1, 2, 3, and 4,respectively). Also assume that subscribers 1, 2, 3, and 4 are assignedweights 2, 3, 4, and 1, respectively. Thus, according to the definedweighting, subscriber 1 is generally allocated twice as much powerrelative to subscriber 4, and subscriber 3 is generally allocated twiceas much power as subscriber 1.

For illustrative purposes, U_(i) and W_(i) represent the unweighted andweighted power vectors at iteration “i”, respectively. Initially, theDRA logic 63 divides the initial power values by their associatedweights, yielding weighted powers of {2.5, 2.667, 2.5, 4} forsubscribers {1, 2, 3, 4}, respectively. Thus, subscriber 3 goes from thelargest unweighted power to the smallest weighted value. In the currentexample, U₁ is {5, 8, 10, 4} for subscribers {1, 2, 3, 4}, respectively,and W₁ is {5/W₁, 8/W₂, 10/W₃, 4/W₄} or in other words {2.5, 2.667, 2.5,4} for subscribers {1, 2, 3, 4}, respectively.

The distribution of power is performed by first effectively “pouring”power into or allocating power units to the lowest weighted powersubscribers, which are subscribers 1 and 3 having weighted powers of 2.5in this example, until the power for each of these subscribers is evenwith the next lowest weighted power subscriber (i.e., subscriber 2having a weighted power of 2.667 in this example) or until all of theavailable power units are allocated. Once the powers for the lowestweighted power subscribers are even with the next lowest weighted powersubscriber, the weights are adjusted to reflect the additional powerallocated to the lowest weighted power subscribers in the currentiteration. Specifically, the weighted value for each of the lowestweighted power subscribers is increased by the difference of suchsubscriber's weighted value and the weighted value of the next lowestweighted power subscriber multiplied by the subscriber's originalweighted value. Thus, U₂ is {5+(2.667−2.5)*W₁, 8, 10+(2.667−2.5)*W₃, 4}or in other words {2.667, 2.667, 2.667, 4} for subscribers {1, 2, 3, 4},respectively, and W₂ is {6.666/W₁, 10/W₂, 13.333/W₃, 4/W₄} or in otherwords {3.333, 3.333, 3.333, 4} for subscribers {1, 2, 3, 4},respectively.

For the next iteration, power is effectively “poured” into or allocatedto the lowest weighted power subscribers, which are subscribers 1, 2,and 3 having weighted powers of 2.667 for the current iteration in thisexample, until the power for each of these subscribers is even with thenext lowest weighted power subscriber (i.e., subscriber 4 having aweighted power of 4 in this example) or until all of the available powerunits are allocated. In the current example, the maximum number of powerunits to be allocated across all K frames is 34, and there are only 7available power units to allocate for the current frame. Thus, theprocess ends before subscribers 1-3 reach the weighted power ofsubscriber 4. In this example, the resulting weighted power is {3.333,3.333, 3.333, 4} for subscribers {1, 2, 3, 4}, respectively. FIG. 12shows the iterations of the weighted power, and FIG. 13 shows thecorresponding iterations of the unweighted power. Note that in FIG. 13,subscriber 3 starts with the highest initial power and is increased themost because it has the highest weight. Note also that subscriber 4 isnot allocated any additional power and therefore would not transfer anydata during the current frame.

It should be further noted that, in allocating timeslots to a givensubscriber, there are several considerations that can be taken intoaccount by the DRA logic 63, particularly when the subscriber isallocated an insufficient amount of power for all of its otherwiseavailable timeslots in a frame. In this regard, in allocating one ormore timeslots to a given subscriber, the DRA logic 63 is configured toselect either upstream or downstream based on the subscriber's currenttraffic demand.

For example, if there is data to transmit in only one direction for agiven subscriber, then the DRA logic 63 may allocate to the subscriberactive timeslots only in such direction. As an example, if a givensubscriber is allocated enough power to transmit three timeslots in theupstream direction when there is no data to transmit in the downstreamdirection, then the DRA logic 63 may be configured to allocate threeactive upstream timeslots to the subscriber and no active downstreamtimeslots to the subscriber.

If there is data to transmit in both directions, then the DRA logic 63can be configured to allocate power between upstream and downstream invarious ways. In one exemplary embodiment, the DRA logic 63 isconfigured to allocate power between upstream and downstream timeslotsbased on (e.g., in proportion to) the number of possible upstream anddownstream timeslots in the current frame. As an example, if there aretwice as many downstream timeslots in the downstream block as comparedto the number of upstream timeslots in the upstream block, then the DRAlogic 63 may be configured to allocate to the subscriber twice as manyactive downstream timeslots relative to the number of active upstreamtimeslots allocated to the subscriber.

In another embodiment, the DRA logic 63 is configured to allocate powerbetween upstream and downstream timeslots based on (e.g., in proportionto) the amount of data queued for transmission in the downstreamdirection relative to the amount of data queued for transmission in theupstream direction. For example, if there is twice as much data queuedfor transmission in the downstream direction relative to the amount ofdata queued for transmission in the upstream direction, then the DRAlogic 63 may be configured to allocate to the subscriber twice as manyactive downstream timeslots relative to the number of active upstreamtimeslots allocated to the subscriber. In other embodiments, othertechniques and/or some combination of the aforementioned techniques maybe used to allocate power between the upstream and downstream timeslots.In all cases, the required sum powerK_(d,i)*N_(d,l,j)+K_(u,j)*N_(u,l,j,)for downstream and upstream shouldbe equal to or smaller than the power allocated to the i^(th) subscriberin the j^(th) frame.

For several of the exemplary embodiments described above, it is assumedthat the DRA logic 63 at the service unit 15 is capable of communicatingcontrol information with the CP transceivers 22 and assigning theupstream timeslots. However, for some embodiments, it is possible foreach CP transceiver 22 to implement DRA logic for allocating activeupstream timeslots for the transceiver 22. In one exemplary embodiment,a CP transceiver 22 uses similar criterion as is described above asbeing use by the DRA logic 63 at the service unit 15 in order to assignactive upstream timeslots. Specifically, each CP transceiver 22 isprovisioned with a maximum upstream average power per frame, and thecriterion is:

$P_{u,i} \geq {\frac{1}{K}{\sum\limits_{j = {F - K + 1}}^{F}\; {K_{u,i}N_{u,i,j}}}}$

This is sub-optimal to the case where both the upstream and downstreamallocation are controlled by the DRA logic 63 at the service unit 15,and it generally does not take advantage of other CP transceivers 22that are not using all of their allocated power. An advantage is that itdoes not request the service unit 15 to have knowledge of upstreamtraffic load. It does control the average power while allowing the datatransfer to peak above the average load.

It should be emphasized that the embodiments described herein areexemplary, and various changes and modifications to the embodimentsillustrated herein are possible. The power optimization techniquesdescribed herein may be used with any network device having transceiversfor communicating data across a plurality of subscriber lines.

1. A network service unit, comprising: a plurality of transceiversrespectively coupled to a plurality of subscriber lines; an interfacecoupled to a network connection and configured to receive a data streamfrom the interface; a multiplexer configured to multiplex the datastream and to transmit packets of the data stream to the plurality oftransceivers; and dynamic rate allocation (DRA) logic configuredallocate power among the plurality of transceivers such that an averagepower dissipated by at least the plurality of transceivers during a timeinterval is below a specified power limit, the DRA logic furtherconfigured to allocate timeslots for frames communicated across thesubscriber lines based on the allocated power.
 2. The network serviceunit of claim 1, further comprising a temperature sensor, wherein thespecified power limit is based on a temperature sensed by thetemperature sensor.
 3. The network service unit of claim 1, wherein theDRA logic is configured to determine a value indicative of an amount ofpower available for powering components of the network service unit, andwherein the specified power limit is based on the value.
 4. The networkservice unit of claim 1, further comprising memory for storing dataindicating weights assigned to subscribers serviced by the networkservice unit, wherein the DRA logic is configured to allocate the poweramong the plurality of transceivers based on the weights.
 5. The networkservice unit of claim 1, wherein the DRA logic is configured to allocatethe power among the plurality of transceivers based on a valueindicative of an amount of traffic queued for transmission across atleast one of the subscriber lines.
 6. The network service unit of claim1, wherein the DRA logic is configured to permit peak power dissipationby the network service unit above the specified power limit.
 7. Anetwork service unit, comprising: a plurality of transceiversrespectively coupled to a plurality of subscriber lines; an interfacecoupled to a network connection and configured to receive a data streamfrom the interface; a multiplexer configured to multiplex the datastream and to transmit packets of the data stream to the plurality oftransceivers; and dynamic rate allocation (DRA) logic configured toensure that an average power dissipated by at least the plurality oftransceivers during a time interval is below a specified power limit bycontrolling, based on the specified power limit, allocation of timeslotsfor frames communicated across the subscriber lines by the transceivers.8. The network service unit of claim 7, further comprising a temperaturesensor, wherein the specified power limit is based on a temperaturesensed by the temperature sensor.
 9. The network service unit of claim7, wherein the DRA logic is configured to determine a value indicativeof an amount of power available for powering components of the networkservice unit, and wherein the specified power limit is based on thevalue.
 10. The network service unit of claim 7, further comprisingmemory for storing data indicating weights assigned to subscribersserviced by the network service unit, wherein the DRA logic isconfigured to allocate the power among the plurality of transceiversbased on the weights.
 11. The network service unit of claim 7, whereinthe DRA logic is configured to allocate the power among the plurality oftransceivers based on a value indicative of an amount of traffic queuedfor transmission across at least one of the subscriber lines.
 12. Thenetwork service unit of claim 7, wherein the DRA logic is configured topermit peak power dissipation by the network service unit above thespecified power limit.
 13. A network service unit, comprising: aplurality of transceivers respectively coupled to a plurality ofsubscriber lines; an interface coupled to a network connection andconfigured to receive a data stream from the interface; a multiplexerconfigured to multiplex the data stream and to transmit packets of thedata stream to the plurality of transceivers; a temperature sensor; anddynamic rate allocation logic configured to control, based on atemperature sensed by the temperature sensor, allocation of timeslotsfor frames communicated across the subscriber lines by the transceivers.14. A method, comprising: receiving data at a network service unit, thenetwork service unit coupled to at least one network connection and aplurality of subscriber lines; transmitting the data from a plurality oftransceivers at the network service unit across the plurality ofsubscriber lines; ensuring that an average power dissipated by at leastthe plurality of transceivers during a time interval is below aspecified power limit, wherein the ensuring comprises allocatingtimeslots for frames communicated across the subscriber lines based onthe specified power limit.
 15. The method of claim 14, furthercomprising sensing a temperature at the network service unit, whereinthe specified power limit is based on the sensing.
 16. The method ofclaim 14, further comprising determining a value indicative of an amountof power available for powering components of the network service unit,wherein the specified power limit is based on the value.
 17. The methodof claim 14, further comprising storing, in memory, data indicatingweights assigned to subscribers serviced by the network service unit,wherein the allocating is based on the weights.
 18. The method of claim14, further comprising determining a value indicative of an amount oftraffic queued for transmission across at least one of the subscriberlines, wherein the allocating is based on the value.
 19. The method ofclaim 14, further comprising permitting peak power dissipation by thenetwork service unit above the specified power limit.